Ch.13 - Diffusion And Osmosis Flashcards
What is a selectively permeable membrane?
A selectively permeable membrane allows some but not all molecules to pass through.
What is diffusion?
Diffusion is the spreading out of molecules from a region of high concentration to a region of low concentration
What is osmosis?
Osmosis is the movement of water molecules across a semi-permeable membrane from a region of high water concentration of water to a region of low water concentration.
What happens when an animal cell is in a solution that is the same concentration as their cytoplasm?
If an animal cell is in a solution that is the same concentration as its cytoplasm, water will move in and out of the membrane at the same rate. The volume of the cell will remain the same. It is the job of the kidney to ensure that plasma has the same concentration as blood cells.
What happens when an animal cell is in a less concentrated solution than itself?
If an animal cell is in a solution that is less concentrated than the cell, water will move into the cell due to osmosis. The cell will enlargen and could burst.
How can an animal cell avoid bursting after osmosis?
Amoeba has a lower water concentration than ponds and pools. The osmoregulation system in amoeba consists of a contractile vacuole. The contractile vacuole expels water, which prevents cells from bursting.
What happens if an animal cell is in a solution that is more concentrated than itself?
If an animal cell is in a solution that is more concentrated than the cell, water will move out of the cell due to omosis. This will cause the cell to shrivel and possibly die, this is a condition known as crenation.
What is the cell wall permeable to?
The cell wall is fully permeable to water, gases and many solutes (salt, sugar).
What happens when a plant cell when is in a solution less concentrated than itself?
If a plant cell has a higher concentration of solute than its surroundings, water moves into the cytoplasm and vacuole of the cell by osmosis. This is how plant roots absorb water from the soil.
What is turgor pressure?
Turgor pressure is the outward pressure of the cytoplasm and vacuole against the cell wall of a plant. This gives the cell strength.
What happens when a plant cell is in a solution more concentrated than itself?
If the surrounding are more concentrated than the cell contents, then water moves out of the cell due to osmosis. This induces plasmolysis.
What is plasmolysis?
Plasmolysis is the loss of water from the cytoplasm and the movement of the cell membrane away from the cell wall. The cell looses turgor and strength and is said to be flaccid. When all of the cells in a plant are plasmolysed, it is said to wilt. For example, when cut flowers lose water due to evaporation.
What is deplasmolysis?
Deplasmolysis is when plasmolysed cells are restored to normal by placing them in a less concentrated solution.
How is osmosis used to preserve food?
Osmosis is often used to prevent micro-organisms such as bacteria from growing on food. For example, fish and bacon may be soaked in a very salty solution, any micro-organisms in or on the food will die of osmosis. Jams have high sugar concentration so that the micro-organisms are dehydrated and stunted.
